The Interactive Protocol for Digital Multisignature

Abstract

A multisignature scheme has been proposed by Harn in 1994 which requires a broadcast channel in order to prevent signature forgery. This paper proposes an interactive protocol which allows all signers to reach a synchronous mode by generating commitments first and then each signer needs to verify the authenticity of all other signers’ commitments before signing any individual signature. The protocol can be proceeded in any order. After all signers having signed the same message, a multisignature can be computed by the very last signer by combining all individual signatures. The length of multisignatures is always constant and does not depend on the number of signers involved. Anyone can verify this multisignature very efficiently by using the product of all signers’ public keys.